Cadmium Accumulation and Regulation in the Freshwater Mussel .

Cadmium (Cd) pollution poses a serious threat to freshwater ecosystems. The freshwater mussel is increasingly used as a bioindicator for monitoring Cd pollution in aquatic environments. However, the primary routes of Cd accumulation in remain unclear, and the molecular regulatory mechanisms underlying Cd accumulation are poorly understood. To address these gaps, this study employed a novel stable isotope dual-tracer technique to trace Cd from water (waterborne Cd) and the green alga (dietary Cd) during the simultaneous exposure experiment. Comparative transcriptomic analysis was then conducted to characterize molecular responses in following Cd exposure. The results showed that although newly accumulated Cd and Cd increased with exposure concentration and duration, the relative importance of Cd (91.6 ± 2.8%) was significantly higher than that of Cd (8.4 ± 2.8%) ( < 0.05). Cd exposure induced differentially expressed genes primarily enriched in the metabolic processes, cellular processes, and/or the ubiquitin-mediated proteolysis pathway. Within the ubiquitin-mediated proteolysis pathway, TRIP12 (E3 ubiquitin-protein ligase TRIP12) and Cul5 (cullin-5) were significantly upregulated. The findings will provide critical insights for interpreting Cd biomonitoring data in freshwater environments using mussels as bioindicators.